Up to now, a display device such as a television includes a liquid crystal display device using a liquid crystal display panel.
The liquid crystal display device used for the television includes, for example, a transmissive liquid crystal display panel, and a light source (backlight unit) is disposed behind the liquid crystal display panel.
The backlight unit is formed of, for example, a fluorescent tube such as a cold cathode fluorescent tube (CFL). The backlight unit using the fluorescent tube is classified into a direct type and an edge light type according to a position at which the fluorescent tube is arranged.
The direct backlight unit has plural fluorescent tubes arranged at the back of an image display area of the liquid crystal display panel, that is, in an area that is superimposed on the image display area. Also, a reflector is disposed at the back of the fluorescent tube viewed from the liquid crystal display panel. Also, optical parts such as an optical diffuser and an optical sheet are disposed between the liquid display panel and the fluorescent tube.
The direct backlight unit converts linear lights from the fluorescent tubes into a planar light by the optical member, and irradiates the image display area of the liquid crystal display panel with the light. In this situation, the number of fluorescent tubes, the intervals of the fluorescent tubes, and the positions of the optical members are generally determined so as to make the distribution of the brightness of the image display area uniform.
However, on the other hand, there may be required a backlight unit that exhibits a distribution in which the brightness in the vicinity of the center of the image display area in the vertical direction is high, and the brightness at the upper and lower ends of the image display area is low. As an arranging method that meets the above requirement, for example, there has been proposed a method in which the fluorescent tubes are arranged in such a manner that the intervals of the fluorescent tubes in the vicinity of the center in the vertical direction are narrower than the intervals of the fluorescent tubes at the upper and lower end portions (for example, refer to Japanese Patent Laid-Open No. 2002-82626).